This invention is an improved control system for a passenger loading bridge through which passengers walk to board or deplane an airplane and an improved method of operating a loading bridge.
Modern airports are constructed so that passengers walk between full sized commercial airplanes and a terminal building through a loading bridge. The loading bridge is normally retracted adjacent the terminal building when not in use. When an airplane is at a loading location, the loading bridge is driven by an operator so the passageway through the loading bridge aligns with the airplane door and is close enough to the airplane so passengers can safely walk between them.
Conventional loading bridges are self propelled by suitable electric motors under the control of an operator located inside the loading bridge. A major disadvantage of conventional loading bridges is the operator station is inside the loading bridge a few feet from the open end of the runway. Although there are windows adjacent the operator""s station, the operator has relatively poor visibility in all directions except straight out the windows. As a practical matter, the bridge operator must have some additional input in order to align the loading bridge and the airplane door in a safe, repeatable manner.
In practice, a person on the ground adjacent the airplane stands in front of the open runway end in the intended path of the loading bridge or in plain sight adjacent the window and, with hand signals, directs the operator left or right, forward or back. When the loading bridge comes within a few feet of the airplane door, the person giving directions must move out of the way or become pinned between the loading bridge and the airplane. Thus, in the last five feet or so of movement of the loading bridge, the bridge operator can only see down the runway or out the window.
Even though loading bridge operators do their best to position the loading bridge adjacent the airplane door and not damage the airplane, collisions occur with distressing regularity. The damage that can occur is not only to the airplane door or the structural components adjacent the door. Many airplanes have pitot tubes or other sensors on the outside of the airplane in locations that can be impacted by a moving loading bridge.
A major United States airline, operating flights from about a thousand gates, has one collision a week between a loading bridge and an airplane. The cost of these collisions varies substantially, as one would expect. The cost of repairing the airplane runs from a few hundred dollars to several tens of thousands of dollars. Often, the airplane cannot be flown with passengers until repairs are made, causing flights to be cancelled for at least a day and occasionally as much as a week. The total cost of a collision includes the cost of repair, lost revenue while the plane is out of service, the cost of ferrying the plane to a repair location or the cost of ferrying mechanics and parts to the airplane and the like. The total cost of a collision, including lost revenue, is normally much greater than the parts and labor necessary to repair the airplane.
Similar problems occur when retracting the loading bridge. The parking sites for airplanes are selected and marked on the tarmac so planes will not run into the loading bridge when the loading bridge is fully retracted. It occasionally happens that loading bridges are not fully retracted because the bridge operator cannot see whether it is completely docked and planes run into the loading bridge, it also occasionally happens that loading bridges are not fully retracted but are retracted enough to handle the normal plane that appears at a gate. When a different, larger plane taxis up to the gate, they will occasionally hit a loading bridge that is retracted enough for planes that normally use the gate. These collisions are Particularly expensive to repair because the plane is large, heavy and moving.
Another category of collisions occurs when the loading bridge is in the process of being retracted from its operative position toward its stowed position. Sometimes, the loading bridge backs into objects temporarily left under the loading bridge such as baggage carts, generator vehicles, or the like. In some situations, there are physical connections between the loading bridge and the airplane, such as electrical supply conduits. If these are not uncoupled and retracted before the loading bridge starts to move, the airplane can be damaged by the uncoupled physical connections. In brief, there are numerous ways for an airplane or other equipment to be damaged or people to be hurt because the loading bridge operator has poor visibility.
The straight forward solution to this problem is to provide cameras and sensors reporting to an operator""s station so the operator can view various parts of the loading bridge, the airplane and the like, as shown in exemplary U.S. Pat. Nos. 3,683,440 and 5,226,204.
In this invention, a deadman switch is provided on a tether on the outside of the loading bridge under the control of the person on the ground, often called a ramp agent, who normally gives hand signals to the loading bridge k operator. So long as the switch is held in a predetermined position, the control circuit leading to the loading bridge motors work normally. When the switch is released or moved to another position, the control circuit is interrupted or otherwise manipulated to stop the loading bridge for movement in directions which will cause collisions with the airplane.
Thus, in a preferred embodiment, the ramp agent giving signals holds the deadman switch closed while standing below the airplane door or in plain sight through a window and directs the loading bridge operator with suitable hand signals. When the loading bridge approaches the airplane so it is no longer safe to stand in front of the runway, the person giving directions stands aside, holding the switch closed. If the loading bridge continues to move in a safe manner, the person on the ground continues to hold the switch closed. In the event it appears to the person on the ground that the loading bridge is in danger of running into the airplane, the person lets loose of the switch, causing the loading bridge to stop. In this manner, the person who is closest to the scene and who has the best view has the power to stop the loading bridge immediately.
The deadman switch of this invention preferably also operates when moving the loading bridge in a retracting direction so the person on the ground can prevent damages to the airplane and/or to people or equipment behind or underneath the loading bridge during movement of the loading bridge.
It is an object of this invention to provide an improved loading bridge.
A further object of this invention is to provide an improved method of moving a loading bridge.
A further object of this invention is to provide an improved control system for a loading bridge.
A more specific object of this invention is to provide a switch for a loading bridge control system which requires an additional person to hold the switch in a predetermined position to allow the loading bridge to move.
These and other objects and advantages of this invention will become more apparent as this description proceeds, reference being made to the accompanying drawings and appended claims.